Electronic device display with switchable film structures

ABSTRACT

An electronic device may generate content that is to be displayed on a display. The display may have an array of liquid crystal display pixels for displaying image frames of the content. The display may be operated in at least a normal viewing mode, a privacy mode, an outdoor viewing mode, and a power saving mode. The different view modes may exhibit different viewing angles. In one configuration, the display may include a backlight unit that generates a collimated light source and that includes a switchable diffuser film for selectively scattering the collimated light source depending on the current viewing mode of the display. In another configuration, the display may include a backlight unit that generates a scattered light source that includes a switchable microarray structure such as a switchable mirror structure or a tunable microlens array for selectively collimating the scattered light source depending on the current viewing mode.

This application is a continuation of patent application Ser. No.15/051,047, filed Feb. 23, 2016, which claims the benefit of provisionalpatent application No. 62/170,603, filed Jun. 3, 2015, both of which arehereby incorporated by reference herein in their entireties.

BACKGROUND

This relates generally to electronic devices, and more particularly, toelectronic devices with displays.

Electronic devices often include displays. For example, cellulartelephones and portable computers often include displays for presentinginformation to a user.

Liquid crystal displays contain a layer of liquid crystal material.Pixels in a liquid crystal display contain thin-film transistors andpixel electrodes for applying electric fields to the liquid crystalmaterial. The strength of the electric field in a pixel controls thepolarization state of the liquid crystal material and thereby adjuststhe brightness of the pixel.

Conventional liquid crystal displays typically exhibit a fixed viewingangle. For example, a user of the liquid crystal display may be able toview images on the display up to 45 degrees deviation from the normalviewing axis. In certain scenarios, however, it may be desirable toadjust and/or to reduce the viewing angle of the display. Existingsolutions for reducing the viewing angle of liquid crystal displaysinvolve use of an external privacy filter that needs to be mounted overthe display. The use of external privacy filters or other types ofexternal brightness adjustment films may, however, introduce unwantedreflections and glare and are often costly and unwieldy for the user topurchase and maintain.

It would therefore be desirable to be able to provide displays withbuilt-in adjustable light output profiles.

SUMMARY

An electronic device may generate content that is to be displayed on adisplay. The display may be a liquid crystal display have an array ofliquid crystal display pixels. Display driver circuitry in the displaymay display image frames on the array of pixels.

In accordance with an embodiment, the display may include display layershaving display pixels formed from thin-film transistor structures and abacklight unit that emits light through the display layers. Thebacklight unit may be configurable in a first mode in which theelectronic device display exhibits a first viewing angle and in a secondmode in which the electronic device display exhibits a second viewingangle that is different than the first viewing angle.

For example, the display may be operable in a normal viewing mode, aprivacy mode, an outdoor viewing mode, and a power saving mode. Whenoperated in the privacy mode, the display may be limited to at most a30° viewing angle. The normal viewing mode may provide a nominal on-axisluminance level, whereas the outdoor viewing mode may provide anelevated on-axis luminance level that is greater than the nominalon-axis luminance level without actually consuming more power than inthe normal viewing mode. In the power saving mode, the display may alsoprovide the nominal on-axis luminance while actually consuming lesspower than the normal viewing mode.

The backlight unit may include a switchable layer that selectivelyalters the direction of light that is emitted from the backlight unit tothe display layers. In one suitable embodiment, the backlight unitincludes: a light source for generating light, a light guide plate thatreceives the light from the light source and that outputs backlighttowards the display layers, a turning film for collimating the backlightoutput from the light guide plate, and a switchable diffuser film thatreceives the collimated backlight from the turning film and that isconfigured to selectively alter the collimated backlight. The switchablediffuser film is operable in a first state that passes through thecollimated backlight to the display layers and is also operable in asecond state that scatters the collimated backlight.

In another suitable embodiment, the backlight unit may include: a lightsource for generating light, a light guide plate that receives the lightfrom the light source and that outputs backlight towards the displaylayers, and a switchable microarray structure that is selectivelyactivated to collimate the backlight. The switchable microarraystructure may include a switchable mirror structure having a pluralityof gaps that is configured to convert the backlight into an array ofpoint light sources. In one suitable configuration, the switchablemicroarray structure further includes polymer material that is formed onthe switchable mirror structure and that forms pyramid-shaped cavitiessurrounding each of the gaps. In another suitable configuration, theswitchable microarray structure further includes an array of microlenseach of which has a center that is aligned to a respective one of thegaps.

In yet other configurations, the switchable microarray structure may beimplemented using tunable lens structures selected from the groupconsisting of: mechanically driven microlens structures, microfluidicdevices, polymer network liquid crystal (PNLC) based microlensstructures, piezoelectrically driven liquid lens structures, andultrasonic transparent gel based lens structures.

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device suchas a laptop computer with a display in accordance with an embodiment.

FIG. 2 is a perspective view of an illustrative electronic device suchas a handheld electronic device with a display in accordance with anembodiment.

FIG. 3 is a perspective view of an illustrative electronic device suchas a tablet computer with a display in accordance with an embodiment.

FIG. 4 is a perspective view of an illustrative electronic device suchas a computer or other device with display structures in accordance withan embodiment.

FIG. 5 is a cross-sectional side view of an illustrative display inaccordance with an embodiment.

FIG. 6 is a diagram showing how an illustrative display can beconfigured to operate in different viewing modes in accordance with anembodiment.

FIG. 7 is a diagram showing different light output profiles associatedwith the different view modes of FIG. 6 in accordance with anembodiment.

FIG. 8 is a cross-sectional side view of an illustrative backlight unitwith a switchable diffuser in accordance with an embodiment.

FIG. 9 is a cross-sectional side view of an illustrative switchablediffuser having a single layer of polymer dispersed liquid crystal(PDLC) in accordance with an embodiment.

FIG. 10 is a cross-sectional side view of an illustrative switchablediffuser having two layers of PDLC with different droplet sizes inaccordance with an embodiment.

FIG. 11 is a cross-sectional side view of an illustrative switchablediffuser formed using PDLC with asymmetric droplets in accordance withan embodiment.

FIG. 12 is a cross-sectional side view of an illustrative switchablediffuser formed using PDLC with embedded microlens structures inaccordance with an embodiment.

FIG. 13 is a perspective view of an illustrative switchable diffuserformed using switching liquid crystal (LC) lens array structures inaccordance with an embodiment.

FIG. 14 is a cross-sectional side view of an illustrative switchablemicroarray structure for selectively collimating backlight in accordancewith an embodiment.

FIG. 15 is a cross-sectional side view of an illustrative pyramidmicroarray with switchable mirror structures for selectively collimatingbacklight in accordance with an embodiment.

FIG. 16 is a cross-sectional side view of an illustrative microlensarray with switchable mirror structures for selectively collimatingbacklight in accordance with an embodiment.

FIG. 17 is a perspective view of illustrative tunable microlens arraystructures for selectively collimating backlight in accordance with anembodiment.

FIG. 18 is a perspective view of illustrative switchable optical fiberbundle structures for selectively collimating backlight in accordancewith an embodiment.

FIG. 19 is a cross-sectional side view of a display with a switchablephase retarder in accordance with an embodiment.

FIG. 20A is a diagram illustrating a switchable phase retarder in normalviewing mode in accordance with an embodiment.

FIG. 20B is a diagram illustrating a switchable phase retarder inprivacy mode in accordance with an embodiment.

FIG. 21 is a plot of contrast ratio versus phase retardation that isprovided by a switchable phase retarder at a particular viewing angle inaccordance with an embodiment.

FIG. 22 is a plot of phase retardation versus bias voltage for aswitchable phase retarder in accordance with an embodiment.

FIG. 23 is diagram illustrating different viewing angles of a displaypanel in accordance with an embodiment.

FIG. 24A is a diagram of an exemplary display pixel design in accordancewith an embodiment.

FIG. 24B is a cross-sectional side view showing the conductive pixelfingers in accordance with an embodiment.

FIG. 25 is a plot showing regions of low contrast ratio for a displayimplemented using the display pixel design of FIG. 24A in accordancewith an embodiment.

FIG. 26 is a diagram of an improved display pixel design having arotated pixel alignment orientation in accordance with an embodiment.

FIG. 27 is a plot showing regions of low contrast ratio for a displayimplemented using the display pixel design of FIG. 26 in accordance withan embodiment.

FIG. 28 is a diagram of an illustrative single-domain display pixeldesign having a crossbar in accordance with an embodiment.

FIG. 29 is a diagram of an illustrative dual-domain display pixel designwith a crossbar in accordance with an embodiment.

FIG. 30 is a plot of contrast ratio versus viewing angle for a displayimplemented using a display pixel design of the type shown in theembodiments of FIGS. 26, 28, and 29 in accordance with an embodiment.

FIG. 31 is a diagram of a display with multiple electrically controlledbirefringence (ECB) layers in a normal viewing mode in accordance withan embodiment.

FIG. 32 is a diagram of the display of FIG. 31 configured in privacymode in accordance with an embodiment.

FIG. 33 is a plot showing the contrast ratio for the display in FIG. 31in accordance with an embodiment.

FIG. 34 is a plot showing regions of low contrast ratio for the displayin FIG. 32 in accordance with an embodiment.

DETAILED DESCRIPTION

Electronic devices may include displays. The displays may be used todisplay images to a user. Illustrative electronic devices that may beprovided with displays are shown in FIGS. 1, 2, 3, and 4.

FIG. 1 shows how electronic device 10 may have the shape of a laptopcomputer having upper housing 12A and lower housing 12B with componentssuch as keyboard 16 and touchpad 18. Device 10 may have hinge structures20 that allow upper housing 12A to rotate in directions 22 aboutrotational axis 24 relative to lower housing 12B. Display 14 may bemounted in upper housing 12A. Upper housing 12A, which may sometimesreferred to as a display housing or lid, may be placed in a closedposition by rotating upper housing 12A towards lower housing 12B aboutrotational axis 24.

FIG. 2 shows how electronic device 10 may be a handheld device such as acellular telephone, music player, gaming device, navigation unit, watch,or other compact device. In this type of configuration for device 10,housing 12 may have opposing front and rear surfaces. Display 14 may bemounted on a front face of housing 12. Display 14 may, if desired, haveopenings for components such as button 26. Openings may also be formedin display 14 to accommodate a speaker port (see, e.g., speaker port 28of FIG. 2). In compact devices such as wrist-watch devices, port 28and/or button 26 may be omitted and device 10 may be provided with astrap or lanyard.

FIG. 3 shows how electronic device 10 may be a tablet computer. Inelectronic device 10 of FIG. 3, housing 12 may have opposing planarfront and rear surfaces. Display 14 may be mounted on the front surfaceof housing 12. As shown in FIG. 3, display 14 may have an opening toaccommodate button 26 (as an example).

FIG. 4 shows how electronic device 10 may be a display such as acomputer monitor, a computer that has been integrated into a computerdisplay, or other device with a built-in display. With this type ofarrangement, housing 12 for device 10 may be mounted on a supportstructure such as stand 30 or stand 30 may be omitted (e.g., to mountdevice 10 on a wall). Display 14 may be mounted on a front face ofhousing 12.

The illustrative configurations for device 10 that are shown in FIGS. 1,2, 3, and 4 are merely illustrative. In general, electronic device 10may be a laptop computer, a computer monitor containing an embeddedcomputer, a tablet computer, a cellular telephone, a media player, orother handheld or portable electronic device, a smaller device such as awrist-watch device, a pendant device, a headphone or earpiece device, orother wearable or miniature device, a computer display that does notcontain an embedded computer, a gaming device, a navigation device, anembedded system such as a system in which electronic equipment with adisplay is mounted in a kiosk or automobile, equipment that implementsthe functionality of two or more of these devices, or other electronicequipment.

Housing 12 of device 10, which is sometimes referred to as a case, maybe formed of materials such as plastic, glass, ceramics, carbon-fibercomposites and other fiber-based composites, metal (e.g., machinedaluminum, stainless steel, or other metals), other materials, or acombination of these materials. Device 10 may be formed using a unibodyconstruction in which most or all of housing 12 is formed from a singlestructural element (e.g., a piece of machined metal or a piece of moldedplastic) or may be formed from multiple housing structures (e.g., outerhousing structures that have been mounted to internal frame elements orother internal housing structures).

Display 14 may be a touch sensitive display that includes a touch sensoror may be insensitive to touch. Touch sensors for display 14 may beformed from an array of capacitive touch sensor electrodes, a resistivetouch array, touch sensor structures based on acoustic touch, opticaltouch, or force-based touch technologies, or other suitable touch sensorcomponents.

Display 14 for device 10 may include pixels formed from liquid crystaldisplay (LCD) components. A display cover layer may cover the surface ofdisplay 14 or a display layer such as a color filter layer or otherportion of a display may be used as the outermost (or nearly outermost)layer in display 14. The outermost display layer may be formed from atransparent glass sheet, a clear plastic layer, or other transparentmember.

A cross-sectional side view of an illustrative configuration for display14 of device 10 (e.g., for display 14 of the devices of FIG. 1, FIG. 2,FIG. 3, FIG. 4 or other suitable electronic devices) is shown in FIG. 5.As shown in FIG. 5, display 14 may include backlight structures such asbacklight unit 42 for producing backlight 44. During operation,backlight 44 travels outwards (vertically upwards in dimension Z in theorientation of FIG. 5) and passes through display pixel structures indisplay layers 46. This illuminates any images that are being producedby the display pixels for viewing by a user. For example, backlight 44may illuminate images on display layers 46 that are being viewed byviewer 48 in direction 50.

Display layers 46 may be mounted in chassis structures such as a plasticchassis structure and/or a metal chassis structure to form a displaymodule for mounting in housing 12 or display layers 46 may be mounteddirectly in housing 12 (e.g., by stacking display layers 46 into arecessed portion in housing 12). Display layers 46 may form a liquidcrystal display or may be used in forming displays of other types.

Display layers 46 may include a liquid crystal layer such a liquidcrystal layer 52. Liquid crystal layer 52 may be sandwiched betweendisplay layers such as display layers 58 and 56. Layers 56 and 58 may beinterposed between lower polarizer layer 60 and upper polarizer layer54.

Layers 58 and 56 may be formed from transparent substrate layers such asclear layers of glass or plastic. Layers 58 and 56 may be layers such asa thin-film transistor layer and/or a color filter layer. Conductivetraces, color filter elements, transistors, and other circuits andstructures may be formed on the substrates of layers 58 and 56 (e.g., toform a thin-film transistor layer and/or a color filter layer). Touchsensor electrodes may also be incorporated into layers such as layers 58and 56 and/or touch sensor electrodes may be formed on other substrates.

With one illustrative configuration, layer 58 may be a thin-filmtransistor layer that includes an array of pixel circuits based onthin-film transistors and associated electrodes (pixel electrodes) forapplying electric fields to liquid crystal layer 52 and therebydisplaying images on display 14. Layer 56 may be a color filter layerthat includes an array of color filter elements for providing display 14with the ability to display color images. If desired, layer 58 may be acolor filter layer and layer 56 may be a thin-film transistor layer.Configurations in which color filter elements are combined withthin-film transistor structures on a common substrate layer in the upperor lower portion of display 14 may also be used.

During operation of display 14 in device 10, control circuitry (e.g.,one or more integrated circuits on a printed circuit) may be used togenerate information to be displayed on display 14 (e.g., display data).The information to be displayed may be conveyed to a display driverintegrated circuit such as circuit 62A or 62B using a signal path suchas a signal path formed from conductive metal traces in a rigid orflexible printed circuit such as printed circuit 64 (as an example).

Backlight structures 42 may include a light guide plate such as lightguide plate 78. Light guide plate 78 may be formed from a transparentmaterial such as clear glass or plastic. During operation of backlightstructures 42, a light source such as light source 72 may generate light74. Light source 72 may be, for example, an array of light-emittingdiodes.

Light 74 from light source 72 may be coupled into edge surface 76 oflight guide plate 78 and may be distributed in dimensions X and Ythroughout light guide plate 78 due to the principal of total internalreflection. Light guide plate 78 may include light-scattering featuressuch as pits or bumps. The light-scattering features may be located onan upper surface and/or on an opposing lower surface of light guideplate 78. Light source 72 may be located at the left of light guideplate 78 as shown in FIG. 5 or may be located along the right edge ofplate 78 and/or other edges of plate 78.

Light 74 that scatters upwards in direction Z from light guide plate 78may serve as backlight 44 for display 14. Light 74 that scattersdownwards may be reflected back in the upwards direction by reflector80. Reflector 80 may be formed from a reflective material such as alayer of plastic covered with a dielectric mirror thin-film coating.

To enhance backlight performance for backlight structures 42, backlightstructures 42 may include optical films 70. Optical films 70 may includediffuser layers for helping to homogenize backlight 44 and therebyreduce hotspots, compensation films for enhancing off-axis viewing, andbrightness enhancement films (also sometimes referred to as turningfilms) for collimating backlight 44. Optical films 70 may overlap theother structures in backlight unit 42 such as light guide plate 78 andreflector 80. For example, if light guide plate 78 has a rectangularfootprint in the X-Y plane of FIG. 5, optical films 70 and reflector 80may have a matching rectangular footprint. If desired, films such ascompensation films may be incorporated into other layers of display 14(e.g., polarizer layers).

In accordance with an embodiment of the present invention, display 14may be configured to operate in various user viewing modes. FIG. 6 is adiagram showing different viewing modes in which display 14 can beconfigured to operate. As shown in FIG. 6, display 14 may be configuredto operate in at least a normal viewing mode 100, a privacy viewing mode102, an outdoor viewing mode 104, and a power saving mode 106. Undernormal lighting conditions (e.g., when display 14 is used indoors),display 14 may be placed in normal viewing mode 100 that exhibits anominal viewing angle and a nominal display brightness level. When it isdesired to reduce the viewing angle of display 14 below the nominal viewangle, display 14 may be placed in privacy mode 102. Under brightambient lighting conditions (e.g., when display 14 is used outdoors inbright sunny conditions), display 14 may be placed in outdoor viewingmode 104 that boosts the display brightness beyond the nominal level sothat the content on display 14 is more visible to the user. When it isdesired to minimize power consumption of the electronic device, display14 may be placed in power saving mode 106 that exhibits a reduceddisplay brightness level and optionally reduced viewing angle.

FIG. 7 is a diagram plotting average picture luminance versus viewingangle illustrating different light output profiles associated with thedifferent view modes of FIG. 6. As shown in FIG. 7, curve 110 representsthe light output profile for normal view mode 100; curve 112 representsthe light output profile for privacy mode 102; curve 114 represents thelight output profile for outdoor viewing mode 104; and curve 116represents the light output profile for power saving mode 106. Curve 110shows how the normal viewing mode exhibits a relatively wide viewingangle with a cone of vision of greater than 30° (e.g., with a viewingangle of more than 45° or more than 60°). While this may be convenientfor collaborative purposes when display 14 is used to display content toa group of users positioned at varying angles relative to the normalviewing axis, the user may sometimes wish for the display to have a morelimited cone of vision for privacy purposes. Curve 112 shows how theprivacy mode exhibits a substantially reduced viewing angle with aviewing angle of less than 45° or less than 30° (see, curve 112 issubstantially “narrower” than curve 110).

Curve 114 shows how display 14 may be configured to focus its lightoutput to provide a boosted on-axis luminance intensity during brightambient lighting conditions. If desired, curve 114 may exhibit an evennarrower cone of vision than curve 112. By focusing the light towardsthe user without wasting energy emitting light at larger viewing angles,the outdoor viewing mode is able to provide a boosted brightness level(e.g., with up to two times or more of the on-axis luminance intensityof the normal viewing mode) without increasing a net neutral displaypower consumption relative to the normal viewing mode. Curve 116 showshow display 14 may be configured to save power by also reducing theviewing angle without compromising on the brightness level along thenormal viewing axis. In certain embodiments, power saving mode 106 maybe similar or identical to privacy mode 102 and/or outdoor mode 104,except the on-axis luminance level for the outdoor mode may be higher tofacilitate the display of content in sunny conditions.

In accordance with an embodiment, the different display modes describedabove may be implemented using a switchable diffuser film in thebacklight unit. FIG. 8 is a cross-sectional side view showing howbacklight unit 42 may be provided with a switchable diffuser. As shownin FIG. 8, backlight unit 42 may include a light source 72 (e.g., an LEDlight source) for emitting light 74 into light guide plate 78, abrightness enhancement film such as a turning film 202, and a switchablediffuser film 200. Switchable diffuser 200 may be configured in an onstate, an off state, or optionally one or more intermediate states forenhanced tunability.

In the embodiment of FIG. 8, light guide plate 78 may include lightscattering features for emitting a generally scattered light source 210upwards in direction Z. Turning film 202 may serve to convert scatteredlight 210 into a collimated light source 212. The use of turning filmsas part of the backlight unit is generally relatively rare in the artsince turning films output a light source with a fairly limited cone ofvision, which is oftentimes unsuitable for use in normal electronicdevice displays. Turning film 202 can, however, be paired withswitchable diffuser 200 to either generate scattered light 220 whenswitchable diffuser 200 is the off state or to pass through the focusedlight 222 when switchable diffuser 200 is in the on state. Theconfiguration of the different display modes in FIG. 6 can therefore becontrolled by adjusting the state of switchable diffuser 200 (e.g.,diffuser 200 can be turned off to place the display in normal viewingmode or can be turned on to place the display in one of modes 102, 104,or 106).

FIG. 9 is a cross-sectional side view of an illustrative switchablediffuser film 200 having a single layer of polymer dispersed liquidcrystal (PDLC) in accordance with an embodiment. As shown in FIG. 9,liquid crystal droplets 254 may be dispersed in a layer of polymer 256between transparent substrates 250-1 and 250-2. Substrates 250-1 and250-2 may be formed from glass, plastic, or other transparent substratematerial. Transparent conductive materials such as a layer of indium tinoxide (ITO) 252 may be formed on each of substrates 250-1 and 250-2 tocontrol the behavior of the PDLC. In the example of FIG. 9, a voltagesource 258 may be used to apply some amount of voltage onto layers 252to control the orientation of the liquid crystal material in droplets254. For example, switchable diffuser 200 may be placed in the off statewhen no voltage is applied or may be placed in the on state when anominal voltage level is applied. If desired, an intermediate voltagelevel that is between zero volts and the nominal high voltage level maybe applied to fine tune the optical behavior of diffuser film 200 toplace display 14 in a selected one of the user viewing modes (e.g., thedifferent viewing modes as described in connection with FIG. 6).

FIG. 10 shows another suitable arrangement in which switchable diffuser200 is provided with two layers of PDLC. As shown in FIG. 10, liquidcrystal droplets 254-1 formed between transparent substrates 250-1 and250-2 may have a first size, whereas liquid crystal droplets 254-2formed between transparent substrates 250-2 and 250-3 may have a secondsize that is different than the first size. A first voltage source 258-1may be used to control the behavior of droplets 254-1, whereas a secondvoltage source 258-2 may be used to control the behavior of droplets254-2. For example, display 14 may be placed in the normal viewing modeby turning off both voltage sources 258-1 and 258-2. Display 14 may beplaced in the privacy mode by turning on only voltage source 258-1, inthe outdoor mode by turning on only voltage source 258-2, or in thepower saving mode by turning on both voltage sources 258-1 and 258-2.This example is merely illustrative. If desired, voltage sources 258-1and 258-2 can be tuned individually to provide the desired light outputprofile for each of the various user viewing modes.

FIGS. 11 and 12 show other suitable arrangements of the switchablediffuser film 200. As shown in FIG. 11, the switchable diffuser film maybe provided with asymmetric droplets 255. As shown in FIG. 12, theswitchable diffuser may be provided with embedded microlens structures260 for further control of the transmitted light. The microlensstructures 260 of FIG. 12 may not be switchable.

The different embodiments of FIGS. 9-12 for implementing a switchablediffuser film using PDLC is merely illustrative and do not serve tolimit the scope of the present invention. If desired, switchablediffuser film 200 may be implemented using polymer network liquidcrystal (PNLC) material, polymer stabilized cholesteric texture (PSCT)material, a combination of these materials, and/or other suitableadjustable light diffusing materials.

In another suitable arrangement, the switchable diffuser film may alsobe implemented using a switchable liquid crystal (LC) lens arraystructure (see, e.g., switchable diffuser 200′ in FIG. 13). As shown inFIG. 13, switchable diffuser 200′ may include a first adjustable LC lensarray 290-1 stacked with a second adjustable LC lens array 290-2. Eachlayer of adjustable LC lens array may include rows of cylindrical lenses292 covered with liquid crystal material 294. The cylindricalmicrolenses in layer 290-1 may be formed perpendicular to thecylindrical microlenses in layer 290-2 to help focus light from twoorthogonal directions. In particular, lenses 292 may be polymermicrolenses and may exhibit a “concave-up” orientation for selectivelyscattering light. Layers 290-1 and 290-2 may be provided with patternedelectrodes (e.g., conductive ITO structures) that may be selectivelybiases using voltage sources (not shown) to modulate the opticalproperties of the LC material 294.

For example, a high voltage may be applied across the liquid crystalmaterial 294 so that the liquid crystal material 294 exhibits the sameindex of refraction as the polymer microlenses 292. When microlenses 292and the liquid crystal material 294 are index-matched, no lensing effectis provided and the collimated light 212 from the backlight unit isallowed to pass through substantially unscattered. When a low voltage isapplied across the liquid crystal material 294, the liquid crystalmaterial 294 may exhibit a different refractive index as the polymermicrolenses 292. When the index of refraction of the microlenses 292 andthe liquid crystal material 294 are mismatched, microlenses 292 areeffectively switched into use to scatter the incoming collimatedbacklight 212 to generate a scattered outgoing light 220. This exampleis merely illustrative. In general, any desired amount of voltage can beapplied to the LC material so that switchable diffuser 200′ exhibits thedesired optical transmission/scattering property for each of thedifferent view modes described in connection with FIG. 6. The example ofFIG. 13 in which the microlenses are formed in a regular periodicconfiguration is merely illustrative. If desired, the microlensstructures may be formed with random varying pitches and widths and mayexhibit non-cylindrical shapes.

In certain embodiments, the switchable diffuser may also be implementedusing a switchable optical fiber bundle. As shown in FIG. 18, switchableoptical fiber bundle 400 may include optical fibers 402 made of glass,plastic, or other suitable fiber material bundled together and bondedusing polymer adhesive 404. In one configuration, switchable materialsuch as PDLC or PNLC may be used as the binding material. In anotherconfiguration, the switchable material may be filled within the core ofeach optical fiber. When the switchable material is placed in a firststate, the incoming collimated light 410 may be allowed to pass throughsubstantially unaltered. When the switchable material is placed in asecond state that is different than the first state, the incomingcollimated light 410 may be altered and output as scattered light 412.If desired, the switchable optical fiber bundle 400 may also receivescattered backlight and can be used to selectively output collimatedlight.

In accordance with another embodiment, the different display modesdescribed above may be implemented using a switchable microarraystructure in the backlight unit. FIG. 14 is a cross-sectional side viewshowing how backlight unit 42 may be provided with a switchablemicroarray structure 300 that may be configured in an on state, an offstate, or optionally one or more intermediate states for enhancedtunability.

In the embodiment of FIG. 14, light guide plate 78 may include lightscattering features for emitting a generally scattered light source 210upwards in direction Z. Switchable microarray structure 300 may directlyreceive the scattered light source 210 (without an intervening turningfilm) and may serve to convert the scattered light 210 into a collimatedlight source 304 or may otherwise pass through or further scatter theincoming light 210 to output scattered light 302. The configuration ofthe different display modes in FIG. 6 can therefore be controlled byadjusting the state of switchable microarray structure 300 (e.g.,diffuser 300 can be turned off to place the display in normal viewingmode or can be turned on to place the display in one of modes 102, 104,or 106).

FIG. 15 is a cross-sectional side view of an illustrative pyramidmicroarray with switchable mirror structures for selectively collimatingbacklight in accordance with an embodiment. As shown in FIG. 15,microarray structure 300 may include switchable mirror layer 310 havingopenings 314 and polymer material 316 that is formed over switchablemirror layer 310 and that may be patterned to form pyramid-shapedcavities 312. The cavities 312 may be filled with air or other materialhaving a refractive index that is different than polymer 316.

Switchable mirror layer 310 may be implemented using cholesteric liquidcrystal material, electrochromic material, or other types of materialswith adjustable reflectivity. Similar to the PDLC material, mirror layer310 may be selectively activated using a voltage source (not shown).When mirror 310 is configured in the on state, any backlight strikingmirror 310 will be reflected back down towards reflector 80 (asindicated by path 321) whereas light may only be allowed to travelthrough layer 310 via the gaps 314. Any light that propagates throughthese gaps 314 will be guided by the pyramid-shaped cavities 312 togenerate a collimated light source 320. The switchable mirror 310operated in this way helps to convert the light emit directly from thelight guide plate 78 into an array of point light sources. Lightreflected from the mirror will therefore be recycled through the lightguide and reflector 80, which helps to improve output efficiency. Whenmirror 310 is configured in the off state, mirror 310 will beeffectively switched out of use (e.g., mirror 310 will no longer exhibitreflective capabilities) and light exiting structures 300 will remainuncollimated in the scattered state.

The pyramidal shape of cavities 312 in structure 300 is merelyillustrative. If desired, cavities 312 may be formed with a conicalshape, a trapezoidal shape, or other suitable shapes for guiding andfocusing the light in a way to produce the desired viewing angle whenmirror 310 is switched into use.

FIG. 16 shows yet another suitable arrangement in which structure 300includes a microlens array 330 that is formed over switchable mirrorstructures 310. As shown in FIG. 16, the center of each microlens inarray 330 may be aligned to corresponding gaps 314 in mirror layer 310.When mirror 310 is activated, any backlight striking mirror 310 will bereflected back down towards reflector 80 (as indicated by path 321)while some of the light may travel through layer 310 via openings 314.Any light that propagates through these openings will be focused usingthe microlens structures 330 to generate a collimated light source 321.The switchable mirror 310 operated in this way serves to convert thelight emit from the light guide plate 78 into an array of point lightsources at the gap locations. When switchable mirror 310 is deactivated,mirror 310 will be effectively switched out of use (e.g., mirror 310will no longer exhibit reflective capabilities) and light exitingstructure 300 will remain uncollimated in the scattered state.

In another suitable embodiment, the adjustable microarray structure maybe implemented using a switchable liquid crystal (LC) lens arraystructure (see, e.g., switchable microlens array structure 300′ in FIG.17). As shown in FIG. 17, structure 300′ may include a first adjustableLC lens array 350-1 stacked with a second adjustable LC lens array350-2. Each layer of adjustable LC lens array may include rows ofcylindrical lenses 352 covered with liquid crystal material 354. Thecylindrical microlenses in layer 350-1 may be formed perpendicular tothe cylindrical microlenses in layer 350-2 to help focus light from twoorthogonal directions. In particular, lenses 352 may be polymermicrolenses and may exhibit a “concave-down” orientation for selectivelyfocusing light when the microlenses are switched into use. Layers 350-1and 350-2 may be provided with patterned electrodes (e.g., conductiveITO structures) that can be selectively biases using voltage sources(not shown) to modulate the optical properties of the LC material 354.

For example, a high voltage may be applied across the liquid crystalmaterial 354 so that the liquid crystal material 354 exhibits the sameindex of refraction as the polymer microlenses 352. When the polymermicrolenses 352 and the liquid crystal material 354 are index-matched,no lensing effect is provided and the incoming scattered light 210 fromthe backlight unit is allowed to pass through without being collimated.When a low voltage is applied across the liquid crystal material 354,the liquid crystal material 354 may exhibit a different refractive indexas the polymer microlenses 352. When the index of refraction of themicrolenses 352 and the liquid crystal material 354 are mismatched,microlenses 352 are effectively switched into use to collimate theincoming scattered backlight 210 to generate a collimated outgoing light304. This example is merely illustrative. In general, any desired amountof voltage can be applied to the LC material so that switchablemicroarray structure 300′ exhibits the desired opticaltransmission/scattering property for each of the different view modesdescribed in connection with FIG. 6. The example of FIG. 17 in which themicrolenses are formed in a regular periodic configuration is merelyillustrative. If desired, the microlens structures may be formed withrandom varying pitches and widths and may exhibit non-cylindricalshapes.

The tunable lens structures described in connection with FIGS. 13 and 17are merely illustrative and do not serve to limit the scope of thepresent invention. In yet other suitable embodiments, the tunablemicrolens array structures may be implemented using mechanically drivenmicrolens structures, microfluidic devices, polymer network liquidcrystal (PNLC) based microlens structures, piezoelectrically drivenliquid lens structures (e.g., dynamorph microlenses), ultrasonictransparent gel based lens structures, just to name a few. If desired,these tunable lens structures may be used in conjunction with switchablemirror structures (e.g., mirror 310 of FIGS. 15 and 16) and switchablediffuser film structures (e.g., as part of the embedded microlens array260 of FIG. 12) to provide further tunability in the output lightprofile.

The embodiments described above in which the light output from thebacklight unit is selectively collimated depending on the currentviewing mode effectively reduces the luminance at higher viewing angles(e.g., the display appears darker as the user moves away from the normalaxis of the display panel) and are therefore sometimes referred to asimplementing a “black” mode.

In accordance with another suitable arrangement of the presentinvention, a switchable structure may be placed above the liquid crystaldisplay layer to dynamically adjust the contrast ratio as a function ofthe viewing angle. For example, the switchable structure may beconfigured to reduce the contrast ratio as the user moves away from thenormal axis of the display panel, thereby making the display appearlighter or more faded. Privacy mode implemented by reducing the contrastratio is therefore sometimes referred to as “white” mode.

In accordance with an embodiment, the white privacy mode can beimplemented using a switchable phase retarder that is stacked with theliquid crystal display (LCD) layer. As shown in FIG. 19, display layers26 may include an LCD layer 500 formed between upper polarizer 54 andlower polarizer 60 and a dynamically tunable structure such asswitchable phase retarder layer 502 interposed between upper polarizer54 and LCD layer 500. Layer 500 may, for example, include layers 56, 52,and 58 of FIG. 5.

The exemplary configuration of FIG. 19 in which switchable phaseretarder 502 is formed between upper polarizer 54 and LCD layer 500 ismerely illustrative and does not serve to limit the scope of the presentinvention. If desired, switchable phase retarder 502 may bealternatively formed between lower polarizer 60 and LCD layer 500. Inyet other suitable arrangements, a first switchable phase retarder maybe sandwiched between upper polarizer 54 and LCD layer 500 while asecond switchable phase retarder is sandwiched between bottom polarizer54 and LCD layer 500.

Switchable phase retarder layer 502 may be configured to control thecontrast of the display image at higher, oblique viewing angles (e.g.,from 30° to 90°). Typically, display 14 may include phase compensationfilms such as optical films 70 described in connection with FIG. 5 tosuppress light leakage at large viewing angles (i.e., to help enhanceoff-axis viewing by providing high contrast at wide viewing angles). Byadding an additional switchable phase retarder film such as switchablephase retarder 502 into the display stack, the phase compensationfunction for oblique viewing angles can be adjusted.

Switchable phase retarder 502 may be operable in at least two modes.FIG. 20A shows switchable phase retarder 502 configured in normalviewing mode, whereas FIG. 20B shows switchable phase retarder 502configured in privacy mode (which may also include the outdoor viewingmode and the power saving mode). As shown in FIG. 20, liquid crystalmolecules 514 may be dispersed between transparent substrates 510 and512. Substrates 510 and 512 may be formed from glass, plastic, or othertransparent substrate material. Transparent conductive materials such asa layer of indium tin oxide (ITO) may be formed on each of substrates510 and 512 to control the behavior of molecules 514.

In the example of FIG. 20A, retarder layer 502 may be placed in an offstate when no voltage is applied so that molecules 514 are in anisotropic state. When operated in the isotropic mode, the phase retarderdoes not affect any phase or polarization of the propagating lightbecause the retarder is optically isotropic with visible light; theretarder is therefore effectively switched out of use.

In the example of FIG. 20B, a voltage source may apply some amount ofvoltage across substrates 510 and 512 to create an electric field 516 sothat the molecules are placed in an anisotropic state 514′ (sometimesreferred to as a chiral nematic phase). In the anisotropic mode, lightcoming from on-axis will not experience any phase retardation, and thepolarization of the on-axis light is maintained. However, light passingthrough retarder 502 at oblique angles will experience phaseretardation. As a result, images view on-axis will exhibit high contrastwhile images view from oblique angles will exhibit low contrast. Bycontrolling the voltage applied, the resulting electric field may inducea birefringence in any suitable liquid crystal material via the Kerreffect to switch layer 502 between the two modes. As examples,switchable phase retarder 502 may be implemented using blue phase LCmaterial, discotic phase LC material, bowlic phase LC material,lyotropic LC materials, micellar cubic phase LC materials, hexagonalphase LC material, metallotropic LC material, a combination of thesematerials, and/or other suitable types of switchable material.

FIG. 21 is a plot of contrast ratio versus phase retardation that can beprovided by switchable phase retarder 502 at an exemplary viewing angleof 30° in accordance with an embodiment. As shown by curve 600 in FIG.21, contrast ratio may generally decrease as the amount of phaseretardation is increased. In particular, line 602 may represent athreshold level below which the contrast ratio should be maintained inprivacy mode. For example, a maximum contrast ratio of 1.2 may be deemeda sufficiently low contrast ratio to prevent users from reading thedisplay at viewing angles greater than 30°. In the example of FIG. 21, aminimum phase retardation of 900 nanometers (nm) may be necessary tomaintain the contrast ratio below predetermined threshold 602.

The amount of phase retardation may be controlled by the voltage appliedacross the switchable phase retarder. FIG. 22 is a plot of phaseretardation versus bias voltage for switchable phase retarder 502 inaccordance with an embodiment. As shown by curve 610 in FIG. 22, theamount of phase retardation generally increases as a function of appliedvoltage. To meet the 900 nm phase retardation requirement discussed inconnection with FIG. 21 (as indicated by dotted threshold line 612 inFIG. 22), a minimum bias voltage of 50 V may have to be applied acrossthe switchable phase retarder. Voltages of greater than 50 V may also beapplied to provide extra margin at the expense of power consumption. Theamount of phase retardation and the amount of bias voltage that arerequired to provide the desired contrast ratio shown in FIGS. 21 and 22are merely illustrative and are not intended to limit the scope of thepresent invention. Other threshold contrast levels corresponding toother phase retardation and bias voltage levels may be used to providethe desired amount of privacy.

FIG. 23 is diagram illustrating different viewing angles of a displaypanel. The X-Y axes form a plane that is coplanar with the displaypanel, whereas the Z axis represents a normal axis that is orthogonal tothe plane of the display panel. Angle θ represents a viewing angle fromthe Z axis. If angle ϕ is fixed at zero degrees, then angle θ willcorrespond to the viewing angles illustrated and described in connectionwith FIG. 7. On the other hand, angle ϕ represents a viewing angle inthe X-Y plane. Assuming the display panel is in the upright position onthe tabletop, a viewer's elevation will change as angle ϕ is varied. Ingeneral, it is desirable for a display to exhibit reduced contrastratios for angles θ greater than 30° at an angle ϕ of zero or 180degrees during privacy viewing modes.

FIG. 24A is a diagram of an exemplary display pixel design in accordancewith an embodiment. As shown in FIG. 24A, the display may include pixelelectrodes 700 patterned in a conventional chevron formation, where eachseparate electrode is angled at approximately 80°.

FIG. 24B is a cross-sectional side view of the display pixel circuitryshown in FIG. 24A cut along line AA′. As shown in FIG. 24B, pixelelectrodes 700 (e.g., indium tin oxide electrodes or “fingers”) may beformed on TFT layer 58 (see, e.g., FIG. 5). TFT layer 58 may include TFTcircuitry 722 such as thin-film transistor structures formed over TFTsubstrate 720. Liquid crystal material 52 may formed over pixel fingers700 between TFT layer 58 and color filter layer 56. If desired, theorder of TFT layer 58 and color filter layer 56 can be flipped such thatlight exits the display by passing through color filter layer 56 beforepassing through TFT layer 58.

FIG. 25 is a plot showing regions of low contrast ratio in the X-Y planefor a display implemented using the chevron pixel electrode arrangementof FIG. 24A. As shown in FIG. 25, the lighter regions corresponding todotted axes 702 where angle ϕ is approximately zero or 90 degreesrepresent areas of high contrast, whereas the darker regions 704centered at angles ϕ of approximately 45, 135, 215, and 315 degreesrepresent areas of low contrast. Note that the contrast ratio generallydecreases as one moves away from the center of the plot (i.e., asviewing angle θ increases).

In the example of FIG. 25, the low contrast regions 704 are undesirablyoffset by 45°. As described above, it is generally desirable to alignthe low contrast regions to angles ϕ of zero or 180 degrees since thatwould reduce view-ability from undesired, nearby or adjacent onlookers.In an effort to effectively rotate the contrast profile provided by theswitchable phase retarder, an improved display pixel design is provided(see, e.g., FIG. 26). As shown in FIG. 26, the pixel electrodes 750(sometimes referred to here as conductive “fingers”) are angled at 55°.This difference in finger angle relative to the chevron design of FIG.25 provides the desired rotation. The pixel fingers 750 may be formedfrom indium tin oxide (ITO) or other suitable transparent conductivematerial and may be interconnected using a vertical shorting sidebarmember 752.

FIG. 27 is a plot showing regions of low contrast ratio in the X-Y planefor a display implemented using the rotated pixel finger arrangement ofFIG. 26. As shown in FIG. 26, the low contrast regions 712 have beenaligned to angles ϕ of zero and 180 degrees. Additionally, users viewingfrom directly above and below (i.e., at ϕ of 90 and 270 degrees) willalso perceive the reduced contrast ratio. Configured in this way, thedisplay will be able to provide the desired privacy protection fromviewers sitting laterally with respect to the intended user.

In accordance with another suitable arrangement, FIG. 28 shows a rotatedpixel design having fingers 760 interconnected by a conductive crossbarsuch as ITO crossbar 762. In the example of FIG. 28, crossbar 762 may berelatively thinner than fingers 760 to help improve transmittance. As anexample, the fingers 760 may be 3 microns wide while crossbar 762 may beonly 2 microns wide. The configuration of FIG. 28 may also provide acontrast profile similar to that shown in FIG. 27. The embodiments ofFIGS. 26 and 28 in which all of the conductive fingers are formedparallel to one another are sometimes referred to as a single-domainpixel electrode implementation.

In accordance with yet another suitable arrangement, FIG. 29 shows arotated pixel design having fingers formed at multiple different angles.As shown in FIG. 29, a first group of parallel fingers 770-1 may beformed at an angle of 55°, whereas a second group of parallel fingers770-2 may be formed at angle of 35°. The two groups of fingers 770-1 and770-2 may be shorted using a conductive crossbar such as ITO crossbar772. This configuration in which there are two sets of conductivefingers formed at slightly different angles is sometimes referred to asa dual-domain pixel electrode implementation.

The pixel designs of FIGS. 26, 28, and 29 are merely illustrative andare not intended to limit the scope of the present invention. The pixelelectrodes in FIGS. 26, 28, and 29 can also be formed as part of TFTlayer 58 as shown in FIG. 24B. In general, the display may include pixelelectrode fingers patterned at any suitable angle that yields thecontrast plot of FIG. 27 and may include any number of domains ofparallel fingers.

FIG. 30 is a plot of contrast ratio versus viewing angle for a displayimplemented using a display pixel finger design of the type shown in theembodiments of FIGS. 26, 28, and 29 in accordance with an embodiment. Asshown by curve 790 in FIG. 30, the contrast ratio falls below thethreshold level CR_(Th) for viewing angle θ of greater than 30°. Curve790 in FIG. 30 corresponds to the contrast profile at ϕ of zero degrees.If desired, the crossover point where curve 790 intersects with thedesired privacy threshold level CR_(Th) may be adjusted (e.g., to 45°,60°, etc.) by changing the amount of phase retardation, the amount ofbias voltage, the pixel electrode finger design, the type of switchablephase retarder material, etc.

In accordance with another suitable embodiment, display layers 46 mayalso be provided with electrically controlled birefringence (ECB) layersthat can help provide reduced visibility during privacy mode (which mayalso include the outdoor viewing mode and the power saving mode). FIG.31 is a diagram of a display with multiple electrically controlledbirefringence (ECB) layers in a normal viewing mode in accordance withan embodiment. As shown in FIG. 31, a first ECB cell 802 and a secondECB cell 804 may be interposed between LCD layer 800 and lower polarizer60. Layer 800 may, for example, include layers 56, 52, and 58 of FIG. 5.This is merely illustrative. In another suitable arrangement, first andsecond ECB cells 802 and 804 may be interposed between upper polarizer54 and LCD layer 800. In yet another suitable arrangement, first ECBcell 802 may be interposed between upper polarizer 54 and LCD layer 800while second ECB cell 804 may be interposed between lower polarizer 60and LCD layer 800.

Front polarizer 54 may have an absorption axis (sometimes also referredto as transmittance axis) oriented towards the right of the page,whereas back polarizer 60 may have an absorption axis oriented straightout of the page. During normal viewing mode, the ECB cells may beswitched out of use such that ECB cell 802 exhibits an optical axis 814that is parallel to the absorption axis of upper polarizer 54 while ECBcell 804 exhibits an optical axis 816 that is parallel to the absorptionaxis of lower polarizer 60.

FIG. 32 shows the display layers 46 when privacy mode is engaged.Voltage may be applied to rotate the optical axes of the ECB cells. Asshown in FIG. 32, the optical axis of ECB cell 802 may be rotated to anew orientation 815 (e.g., towards the right of the page but slightly uptowards the front polarizer) that is out of alignment with theabsorption axis of front polarizer 54. Similarly, the optical axis ofECB cell 804 may also be rotated to a new orientation 817 (e.g., out ofthe page but slightly up towards the front polarizer) that is out ofalignment with the absorption axis of back polarizer 60.

FIG. 33 is a plot showing the contrast ratio for the display in FIG. 31during normal user mode. As shown in FIG. 33, the display does notexhibit any reduction in contrast ratio in any direction when the ECBcells are switched out of use. FIG. 34 is a plot showing the contrastratio for the display in FIG. 32 during privacy mode (or outdoor viewingmode or power saving mode). As shown in FIG. 34, the display may exhibithigh contrast for the intended cone of vision 900 while providingsubstantially reduced contrast levels outside region 900. Comparing theprofiles of FIG. 34 with that of FIG. 27, the dual ECB cellimplementation may provide additional privacy since it offers reducedvisibility from all directions.

The dual ECB layer implementation described in connection with FIGS. 31and 32 is merely illustrative and is not intended to limit the scope ofthe present embodiments. If desired, only one ECB layer or more than twoECB layers may be provided in the display. If desired, other types ofnematic display layers may be engaged to help limit the viewability ofthe display to the desired cone of vision. For example, one or moredual-domain ECB cells (e.g., an ECB cell in which the optical axis indifferent regions of the ECB cell tilt in opposite directions but in thesame plane) may also be used within the display.

The foregoing is merely illustrative and various modifications can bemade by those skilled in the art without departing from the scope andspirit of the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. A display, comprising: display layers thatinclude display pixels; a backlight unit configured to output backlighttowards the display layers; and an adjustable layer that is selectivelyactivated to collimate the backlight and that is selectively deactivatedso that the backlight passes through the adjustable layer without beingcollimated.
 2. The display of claim 1, wherein the adjustable layercomprises a plurality of light blocking structures.
 3. The display ofclaim 2, wherein the plurality of light blocking structures comprisereflective structures.
 4. The display of claim 3, wherein the reflectivestructures have adjustable reflectivity.
 5. The display of claim 1,wherein the adjustable layer comprises a plurality of angled structuresconfigured to help collimate the backlight.
 6. The display of claim 1,wherein the adjustable layer comprises a plurality of light collimatingstructures each of which has a first width at a first end and a secondwidth that is different than the first width at a second end opposingthe first end.
 7. The display of claim 1, wherein the adjustable layeris electrically adjustable to collimate the backlight in a privacy mode.8. A display, comprising: display layers that include display pixels; abacklight unit configured to output backlight towards the displaylayers; and an adjustable layer operable to deflect the backlight in afirst manner during a first display mode and operable to deflect thebacklight in a second manner different than the first manner during asecond display mode.
 9. The display of claim 8, wherein the adjustablelayer collimates the backlight during the first display mode.
 10. Thedisplay of claim 9, wherein the adjustable layer does not collimate thebacklight during the second display mode.
 11. The display of claim 8,wherein the backlight passes through the adjustable layer during boththe first and second display modes.
 12. The display of claim 8, whereinthe adjustable layer comprises a plurality of angled structuresconfigured to deflect the backlight in the first manner.
 13. The displayof claim 8, wherein the adjustable layer comprises a plurality of lightcollimating structures each of which has a first width and a secondwidth that is different than the first width.
 14. The display of claim13, wherein the plurality of light collimating structures are formeddirectly on electrically controllable structures.
 15. A display,comprising: display layers that include display pixels; a backlight unitconfigured to output backlight towards the display layers; and aplurality of electrically adjustable light blocking structuresinterposed between the backlight unit and the display layers, whereinthe backlight passes through the plurality of electrically adjustablelight blocking structures during a privacy mode and during a normalviewing mode.
 16. The display of claim 15, wherein the plurality ofelectrically adjustable light blocking structures are configured toprovide a first amount of reflectivity during the privacy mode and toprovide a second amount of reflectivity different than the first amountof reflectivity during the normal viewing mode.
 17. The display of claim15, wherein the plurality of electrically adjustable light blockingstructures are configured to deflect the backlight using a first schemeduring the privacy mode and are configured to deflect the backlightusing a second scheme that is different than the first scheme during thenormal viewing mode.
 18. The display of claim 15, wherein the pluralityof electrically adjustable light blocking structures comprise slantedstructures.
 19. The display of claim 18, wherein the slanted structuresare configured to collimate the backlight during the privacy mode. 20.The display of claim 18, wherein the slanted structures each have atleast two different widths.